class_docstr: A class to open and interact with fits files from SDSS
  
  Parameters
  ----------
  buf : string or file buffer (optional)
      file path, buffer, or url of SDSS spectra fits file
      if None, then initialize an empty instance.
  
  Notes
  -----
  This class only provides access to a subset of the information available
  in the sdss spectra fits file.  The raw fits data can be accessed using
  the fits object directly.  This can be found in the attribute
  ``hdulist``.  For details, please refer to the data description:
  http://www.sdss.org/dr7/dm/flatFiles/spSpec.html
code: def _get_line_strength(self, line):
      lam = LINES.get(line)
      if lam is None:
          lam1 = LINES.get(line + "a")
          ind1 = np.where(
              abs(self.hdulist[2].data["restWave"] - lam1) < 1
          )[0]
  
          lam2 = LINES.get(line + "b")
          ind2 = np.where(
              abs(self.hdulist[2].data["restWave"] - lam2) < 1
          )[0]
  
          if len(ind1) == 0:
              s1 = h1 = 0
              nsig1 = 0
          else:
              s1 = self.hdulist[2].data["sigma"][ind1]
              h1 = self.hdulist[2].data["height"][ind1]
              nsig1 = self.hdulist[2].data["nsigma"][ind1]
  
          if len(ind2) == 0:
              s2 = h2 = 0
              nsig2 = 0
          else:
              s2 = self.hdulist[2].data["sigma"][ind2]
              h2 = self.hdulist[2].data["height"][ind2]
              nsig2 = self.hdulist[2].data["nsigma"][ind2]
  
          strength = s1 * h1 + s2 * h2
          nsig = max(nsig1, nsig2)
      else:
          ind = np.where(
              abs(self.hdulist[2].data["restWave"] - lam) < 1
          )[0]
  
          if len(ind) == 0:
              strength = 0
              nsig = 0
          else:
              s = self.hdulist[2].data["sigma"][ind]
              h = self.hdulist[2].data["height"][ind]
              nsig = self.hdulist[2].data["nsigma"][ind]
              strength = s * h
  
      return strength, nsig
  
imports: import gc
  import numpy
  from scipy.ndimage import gaussian_filter1d, uniform_filter1d
  from scipy import interpolate
  from .None import download_with_progress_bar
label_desc: Use image node_id 18 for calling the SDSSfits obj's underlying member method code with example usage: obj._get_line_strength(line) and returns: strength,  nsig